With increasing demand for more information to be supplied to homes and/or businesses, network providers are constantly adding, expanding, upgrading, and/or switching their networks to improve overall optical communications network(s). Optical communications networks typically offer high-speed voice, video, and data transmission between users, such as providers, residential homes, businesses, government agents, and/or networks. For example, conventional optical networks include, but not limited to, fiber to the node/neighborhood (“FTTN”), fiber to the curb (“FTTC”), fiber to the building (“FTTB”), fiber to the home (“FTTH”), fiber to the premises (“FTTP”), or other edge location to which a fiber network extends.
To increase data capacity with high transmission speed using optical fibers, the optical network deploys wave-divisional multiplexing (“WDM”) optical transmission mechanism. WDM system may include coarse WDM (“CWDM”), dense WDM (“DWDM”), or the like. A feature of WDM system is to allow a single optical fiber to carry multiple channels or wavelengths of optical data.
To route optical signals between various optical nodes or devices, a WDM system, for example, may be employed to handle optical signal routing. The WDM system, for certain applications, is able to multiplex a number of optical signals with different wavelengths onto a single optical fiber. A wavelength may also be referred as a frequency or color capable of traveling across an optical fiber. Different wavelengths, for instance, can be generated by different lasers. With a WDM network environment, a typical fiber may be configured to carry multiple sets of network traffic using different wavelengths. For instance, a fiber can be configured up to 88 channels wherein each channel can transmit a specific type of wavelength containing optical information.
To properly multiplexing and demultiplexing each optical signal or wavelength from WDM transmission, combining and separating processes are required. Since designed incident angle is generally small such as 1.8° (degrees) for DWDM, separation of reflected beam can be difficult. To differentiate wavelengths with small angles, an optical path which is also known as working distance or gap, between the filters and the mirror can be relatively long. For example, for DWDM with channel spacing less than 200 GHz with smaller designed AOI (angle of incidence), such as 3.5° and 1.8°, the optical path (gap between mirror and filters) can be greater than 20 millimeters (>20 mm) in order to couple the separated beam into fibers or fiber collimators.
A problem associated with a compact optical device such as a WDM device is that it is difficult to reduce the overall size of the device due to various limitations such as minimal AOI and optical paths.